Typically in wireless communication systems such as that illustrated in FIG. 1, a base station 102 that transmits to and receives from mobile units 104 is used to create what is termed a cell. In CDMA wireless systems, in particular, optimization is a critical consideration that has significant impact on the performance and capacity of a CDMA system. Particularly in both 2G and 3G CDMA systems, the need to enhance the capacity of the systems is increasing. One method for optimizing capacity in a CDMA cell is to minimize areas suffering from pilot pollution. Typically a base station 102 has a number of antennas, each of which is used to form a respective sector within a CDMA cell. Each CDMA sector sends its own pilot channel requiring its own corresponding pseudo-random noise (PN) offset. If a mobile unit 104 is in a location within the CDMA cell where numerous pilot channels are received with relatively equal signal strength, pilot pollution likely will result. This pollution is detrimental because it may cause dropped calls and decreased capacity. Thus, the more sectors per cell may result in increased pilot pollution.
As the number of sectors per site or cell increases, however, so does the capacity of the system as those illustrated by the table in FIG. 2. As is shown, the increase in capacity from 1 to 12 sectors, for example, is over six times gain and the Erlangs for the site or cell increases from approximately 21 to 134. As mentioned previously, however, the increase in the number of sectors may increase degradation of the CDMA performance due to pilot pollution. A further problem is that more sectors require more antennas, power amplifiers and cables thereby increasing the cost of the system. As an example, a 12 sector system would require 24 receive antennas (i.e., 12 sectors×2 for receive diversity) and 24 transmit antennas (12 sectors×2 for transmit diversity).
Hence, there is a need to increase the capacity of CDMA systems by increasing the number of sectors while decreasing pilot pollution and reducing the cost outlay for system hardware.